Target/SPIRV/SPIRVModuleAnalysis.cpp

//===- SPIRVModuleAnalysis.cpp - analysis of global instrs & regs - C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// The analysis collects instructions that should be output at the module level
// and performs the global register numbering.
//
// The results of this analysis are used in AsmPrinter to rename registers
// globally and to output required instructions at the module level.
//
//===----------------------------------------------------------------------===//

#include "SPIRVModuleAnalysis.h"
#include "SPIRV.h"
#include "SPIRVGlobalRegistry.h"
#include "SPIRVSubtarget.h"
#include "SPIRVTargetMachine.h"
#include "SPIRVUtils.h"
#include "TargetInfo/SPIRVTargetInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/TargetPassConfig.h"

using namespace llvm;

#define DEBUG_TYPE "spirv-module-analysis"

static cl::opt<bool>
    SPVDumpDeps("spv-dump-deps",
                cl::desc("Dump MIR with SPIR-V dependencies info"),
                cl::Optional, cl::init(false));

char llvm::SPIRVModuleAnalysis::ID = 0;

namespace llvm {
void initializeSPIRVModuleAnalysisPass(PassRegistry &);
} // namespace llvm

INITIALIZE_PASS(SPIRVModuleAnalysis, DEBUG_TYPE, "SPIRV module analysis", true,
                true)

// Retrieve an unsigned from an MDNode with a list of them as operands.
static unsigned getMetadataUInt(MDNode *MdNode, unsigned OpIndex,
                                unsigned DefaultVal = 0) {
  if (MdNode && OpIndex < MdNode->getNumOperands()) {
    const auto &Op = MdNode->getOperand(OpIndex);
    return mdconst::extract<ConstantInt>(Op)->getZExtValue();
  }
  return DefaultVal;
}

void SPIRVModuleAnalysis::setBaseInfo(const Module &M) {
  MAI.MaxID = 0;
  for (int i = 0; i < SPIRV::NUM_MODULE_SECTIONS; i++)
    MAI.MS[i].clear();
  MAI.RegisterAliasTable.clear();
  MAI.InstrsToDelete.clear();
  MAI.FuncNameMap.clear();
  MAI.GlobalVarList.clear();
  MAI.ExtInstSetMap.clear();

  // TODO: determine memory model and source language from the configuratoin.
  if (auto MemModel = M.getNamedMetadata("spirv.MemoryModel")) {
    auto MemMD = MemModel->getOperand(0);
    MAI.Addr = static_cast<SPIRV::AddressingModel::AddressingModel>(
        getMetadataUInt(MemMD, 0));
    MAI.Mem =
        static_cast<SPIRV::MemoryModel::MemoryModel>(getMetadataUInt(MemMD, 1));
  } else {
    MAI.Mem = SPIRV::MemoryModel::OpenCL;
    unsigned PtrSize = ST->getPointerSize();
    MAI.Addr = PtrSize == 32   ? SPIRV::AddressingModel::Physical32
               : PtrSize == 64 ? SPIRV::AddressingModel::Physical64
                               : SPIRV::AddressingModel::Logical;
  }
  // Get the OpenCL version number from metadata.
  // TODO: support other source languages.
  if (auto VerNode = M.getNamedMetadata("opencl.ocl.version")) {
    MAI.SrcLang = SPIRV::SourceLanguage::OpenCL_C;
    // Construct version literal in accordance with SPIRV-LLVM-Translator.
    // TODO: support multiple OCL version metadata.
    assert(VerNode->getNumOperands() > 0 && "Invalid SPIR");
    auto VersionMD = VerNode->getOperand(0);
    unsigned MajorNum = getMetadataUInt(VersionMD, 0, 2);
    unsigned MinorNum = getMetadataUInt(VersionMD, 1);
    unsigned RevNum = getMetadataUInt(VersionMD, 2);
    MAI.SrcLangVersion = (MajorNum * 100 + MinorNum) * 1000 + RevNum;
  } else {
    MAI.SrcLang = SPIRV::SourceLanguage::Unknown;
    MAI.SrcLangVersion = 0;
  }

  if (auto ExtNode = M.getNamedMetadata("opencl.used.extensions")) {
    for (unsigned I = 0, E = ExtNode->getNumOperands(); I != E; ++I) {
      MDNode *MD = ExtNode->getOperand(I);
      if (!MD || MD->getNumOperands() == 0)
        continue;
      for (unsigned J = 0, N = MD->getNumOperands(); J != N; ++J)
        MAI.SrcExt.insert(cast<MDString>(MD->getOperand(J))->getString());
    }
  }

  // TODO: check if it's required by default.
  MAI.ExtInstSetMap[static_cast<unsigned>(SPIRV::InstructionSet::OpenCL_std)] =
      Register::index2VirtReg(MAI.getNextID());
}

// Collect MI which defines the register in the given machine function.
static void collectDefInstr(Register Reg, const MachineFunction *MF,
                            SPIRV::ModuleAnalysisInfo *MAI,
                            SPIRV::ModuleSectionType MSType,
                            bool DoInsert = true) {
  assert(MAI->hasRegisterAlias(MF, Reg) && "Cannot find register alias");
  MachineInstr *MI = MF->getRegInfo().getUniqueVRegDef(Reg);
  assert(MI && "There should be an instruction that defines the register");
  MAI->setSkipEmission(MI);
  if (DoInsert)
    MAI->MS[MSType].push_back(MI);
}

void SPIRVModuleAnalysis::collectGlobalEntities(
    const std::vector<SPIRV::DTSortableEntry *> &DepsGraph,
    SPIRV::ModuleSectionType MSType,
    std::function<bool(const SPIRV::DTSortableEntry *)> Pred,
    bool UsePreOrder = false) {
  DenseSet<const SPIRV::DTSortableEntry *> Visited;
  for (const auto *E : DepsGraph) {
    std::function<void(const SPIRV::DTSortableEntry *)> RecHoistUtil;
    // NOTE: here we prefer recursive approach over iterative because
    // we don't expect depchains long enough to cause SO.
    RecHoistUtil = [MSType, UsePreOrder, &Visited, &Pred,
                    &RecHoistUtil](const SPIRV::DTSortableEntry *E) {
      if (Visited.count(E) || !Pred(E))
        return;
      Visited.insert(E);

      // Traversing deps graph in post-order allows us to get rid of
      // register aliases preprocessing.
      // But pre-order is required for correct processing of function
      // declaration and arguments processing.
      if (!UsePreOrder)
        for (auto *S : E->getDeps())
          RecHoistUtil(S);

      Register GlobalReg = Register::index2VirtReg(MAI.getNextID());
      bool IsFirst = true;
      for (auto &U : *E) {
        const MachineFunction *MF = U.first;
        Register Reg = U.second;
        MAI.setRegisterAlias(MF, Reg, GlobalReg);
        if (!MF->getRegInfo().getUniqueVRegDef(Reg))
          continue;
        collectDefInstr(Reg, MF, &MAI, MSType, IsFirst);
        IsFirst = false;
        if (E->getIsGV())
          MAI.GlobalVarList.push_back(MF->getRegInfo().getUniqueVRegDef(Reg));
      }

      if (UsePreOrder)
        for (auto *S : E->getDeps())
          RecHoistUtil(S);
    };
    RecHoistUtil(E);
  }
}

// The function initializes global register alias table for types, consts,
// global vars and func decls and collects these instruction for output
// at module level. Also it collects explicit OpExtension/OpCapability
// instructions.
void SPIRVModuleAnalysis::processDefInstrs(const Module &M) {
  std::vector<SPIRV::DTSortableEntry *> DepsGraph;

  GR->buildDepsGraph(DepsGraph, SPVDumpDeps ? MMI : nullptr);

  collectGlobalEntities(
      DepsGraph, SPIRV::MB_TypeConstVars,
      [](const SPIRV::DTSortableEntry *E) { return !E->getIsFunc(); });

  collectGlobalEntities(
      DepsGraph, SPIRV::MB_ExtFuncDecls,
      [](const SPIRV::DTSortableEntry *E) { return E->getIsFunc(); }, true);
}

// True if there is an instruction in the MS list with all the same operands as
// the given instruction has (after the given starting index).
// TODO: maybe it needs to check Opcodes too.
static bool findSameInstrInMS(const MachineInstr &A,
                              SPIRV::ModuleSectionType MSType,
                              SPIRV::ModuleAnalysisInfo &MAI,
                              unsigned StartOpIndex = 0) {
  for (const auto *B : MAI.MS[MSType]) {
    const unsigned NumAOps = A.getNumOperands();
    if (NumAOps != B->getNumOperands() || A.getNumDefs() != B->getNumDefs())
      continue;
    bool AllOpsMatch = true;
    for (unsigned i = StartOpIndex; i < NumAOps && AllOpsMatch; ++i) {
      if (A.getOperand(i).isReg() && B->getOperand(i).isReg()) {
        Register RegA = A.getOperand(i).getReg();
        Register RegB = B->getOperand(i).getReg();
        AllOpsMatch = MAI.getRegisterAlias(A.getMF(), RegA) ==
                      MAI.getRegisterAlias(B->getMF(), RegB);
      } else {
        AllOpsMatch = A.getOperand(i).isIdenticalTo(B->getOperand(i));
      }
    }
    if (AllOpsMatch)
      return true;
  }
  return false;
}

// Look for IDs declared with Import linkage, and map the imported name string
// to the register defining that variable (which will usually be the result of
// an OpFunction). This lets us call externally imported functions using
// the correct ID registers.
void SPIRVModuleAnalysis::collectFuncNames(MachineInstr &MI,
                                           const Function &F) {
  if (MI.getOpcode() == SPIRV::OpDecorate) {
    // If it's got Import linkage.
    auto Dec = MI.getOperand(1).getImm();
    if (Dec == static_cast<unsigned>(SPIRV::Decoration::LinkageAttributes)) {
      auto Lnk = MI.getOperand(MI.getNumOperands() - 1).getImm();
      if (Lnk == static_cast<unsigned>(SPIRV::LinkageType::Import)) {
        // Map imported function name to function ID register.
        std::string Name = getStringImm(MI, 2);
        Register Target = MI.getOperand(0).getReg();
        // TODO: check defs from different MFs.
        MAI.FuncNameMap[Name] = MAI.getRegisterAlias(MI.getMF(), Target);
      }
    }
  } else if (MI.getOpcode() == SPIRV::OpFunction) {
    // Record all internal OpFunction declarations.
    Register Reg = MI.defs().begin()->getReg();
    Register GlobalReg = MAI.getRegisterAlias(MI.getMF(), Reg);
    assert(GlobalReg.isValid());
    // TODO: check that it does not conflict with existing entries.
    MAI.FuncNameMap[F.getGlobalIdentifier()] = GlobalReg;
  }
}

// Collect the given instruction in the specified MS. We assume global register
// numbering has already occurred by this point. We can directly compare reg
// arguments when detecting duplicates.
static void collectOtherInstr(MachineInstr &MI, SPIRV::ModuleAnalysisInfo &MAI,
                              SPIRV::ModuleSectionType MSType,
                              bool Append = true) {
  MAI.setSkipEmission(&MI);
  if (findSameInstrInMS(MI, MSType, MAI))
    return; // Found a duplicate, so don't add it.
  // No duplicates, so add it.
  if (Append)
    MAI.MS[MSType].push_back(&MI);
  else
    MAI.MS[MSType].insert(MAI.MS[MSType].begin(), &MI);
}

// Some global instructions make reference to function-local ID regs, so cannot
// be correctly collected until these registers are globally numbered.
void SPIRVModuleAnalysis::processOtherInstrs(const Module &M) {
  for (auto F = M.begin(), E = M.end(); F != E; ++F) {
    if ((*F).isDeclaration())
      continue;
    MachineFunction *MF = MMI->getMachineFunction(*F);
    assert(MF);
    for (MachineBasicBlock &MBB : *MF)
      for (MachineInstr &MI : MBB) {
        if (MAI.getSkipEmission(&MI))
          continue;
        const unsigned OpCode = MI.getOpcode();
        if (OpCode == SPIRV::OpName || OpCode == SPIRV::OpMemberName) {
          collectOtherInstr(MI, MAI, SPIRV::MB_DebugNames);
        } else if (OpCode == SPIRV::OpEntryPoint) {
          collectOtherInstr(MI, MAI, SPIRV::MB_EntryPoints);
        } else if (TII->isDecorationInstr(MI)) {
          collectOtherInstr(MI, MAI, SPIRV::MB_Annotations);
          collectFuncNames(MI, *F);
        } else if (TII->isConstantInstr(MI)) {
          // Now OpSpecConstant*s are not in DT,
          // but they need to be collected anyway.
          collectOtherInstr(MI, MAI, SPIRV::MB_TypeConstVars);
        } else if (OpCode == SPIRV::OpFunction) {
          collectFuncNames(MI, *F);
        } else if (OpCode == SPIRV::OpTypeForwardPointer) {
          collectOtherInstr(MI, MAI, SPIRV::MB_TypeConstVars, false);
        }
      }
  }
}

// Number registers in all functions globally from 0 onwards and store
// the result in global register alias table. Some registers are already
// numbered in collectGlobalEntities.
void SPIRVModuleAnalysis::numberRegistersGlobally(const Module &M) {
  for (auto F = M.begin(), E = M.end(); F != E; ++F) {
    if ((*F).isDeclaration())
      continue;
    MachineFunction *MF = MMI->getMachineFunction(*F);
    assert(MF);
    for (MachineBasicBlock &MBB : *MF) {
      for (MachineInstr &MI : MBB) {
        for (MachineOperand &Op : MI.operands()) {
          if (!Op.isReg())
            continue;
          Register Reg = Op.getReg();
          if (MAI.hasRegisterAlias(MF, Reg))
            continue;
          Register NewReg = Register::index2VirtReg(MAI.getNextID());
          MAI.setRegisterAlias(MF, Reg, NewReg);
        }
        if (MI.getOpcode() != SPIRV::OpExtInst)
          continue;
        auto Set = MI.getOperand(2).getImm();
        if (MAI.ExtInstSetMap.find(Set) == MAI.ExtInstSetMap.end())
          MAI.ExtInstSetMap[Set] = Register::index2VirtReg(MAI.getNextID());
      }
    }
  }
}

// Find OpIEqual and OpBranchConditional instructions originating from
// OpSwitches, mark them skipped for emission. Also mark MBB skipped if it
// contains only these instructions.
static void processSwitches(const Module &M, SPIRV::ModuleAnalysisInfo &MAI,
                            MachineModuleInfo *MMI) {
  DenseSet<Register> SwitchRegs;
  for (auto F = M.begin(), E = M.end(); F != E; ++F) {
    MachineFunction *MF = MMI->getMachineFunction(*F);
    if (!MF)
      continue;
    for (MachineBasicBlock &MBB : *MF)
      for (MachineInstr &MI : MBB) {
        if (MAI.getSkipEmission(&MI))
          continue;
        if (MI.getOpcode() == SPIRV::OpSwitch) {
          assert(MI.getOperand(0).isReg());
          SwitchRegs.insert(MI.getOperand(0).getReg());
        }
        if (MI.getOpcode() != SPIRV::OpIEqual || !MI.getOperand(2).isReg() ||
            !SwitchRegs.contains(MI.getOperand(2).getReg()))
          continue;
        Register CmpReg = MI.getOperand(0).getReg();
        MachineInstr *CBr = MI.getNextNode();
        assert(CBr && CBr->getOpcode() == SPIRV::OpBranchConditional &&
               CBr->getOperand(0).isReg() &&
               CBr->getOperand(0).getReg() == CmpReg);
        MAI.setSkipEmission(&MI);
        MAI.setSkipEmission(CBr);
        if (&MBB.front() == &MI && &MBB.back() == CBr)
          MAI.MBBsToSkip.insert(&MBB);
      }
  }
}

struct SPIRV::ModuleAnalysisInfo SPIRVModuleAnalysis::MAI;

void SPIRVModuleAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<TargetPassConfig>();
  AU.addRequired<MachineModuleInfoWrapperPass>();
}

bool SPIRVModuleAnalysis::runOnModule(Module &M) {
  SPIRVTargetMachine &TM =
      getAnalysis<TargetPassConfig>().getTM<SPIRVTargetMachine>();
  ST = TM.getSubtargetImpl();
  GR = ST->getSPIRVGlobalRegistry();
  TII = ST->getInstrInfo();

  MMI = &getAnalysis<MachineModuleInfoWrapperPass>().getMMI();

  setBaseInfo(M);

  processSwitches(M, MAI, MMI);

  // Process type/const/global var/func decl instructions, number their
  // destination registers from 0 to N, collect Extensions and Capabilities.
  processDefInstrs(M);

  // Number rest of registers from N+1 onwards.
  numberRegistersGlobally(M);

  // Collect OpName, OpEntryPoint, OpDecorate etc, process other instructions.
  processOtherInstrs(M);

  return false;
}